Monoket Retard (Isosorbide Mononitrate)

Monoket Retard is indicated for several cardiovascular conditions where nitrate‑mediated vasodilation improves myocardial oxygen balance.

• Chronic stable angina pectoris: reduces frequency of angina attacks by lowering cardiac workload.
• Heart failure: improves symptoms by decreasing preload and afterload.
• Hypertension: contributes to blood‑pressure reduction through arterial dilation.

• Isosorbide mononitrate is a prodrug that is metabolized to nitric oxide. The released nitric oxide activates guanylate cyclase in vascular smooth muscle, increasing cyclic GMP levels, which leads to relaxation of both venous and arterial vessels. This vasodilation reduces cardiac preload and afterload, enhancing myocardial oxygen supply while lowering systemic blood pressure.

Adverse reactions may vary in frequency and severity.

Common Side Effects

• Headache: throbbing or pressure‑type pain.
• Dizziness or light‑headedness: often related to blood‑pressure fall.
• Flushing: warm sensation with reddening of skin.
• Nausea: mild gastrointestinal upset.
• Palpitations: awareness of heartbeat.
• Hypotension: mild drop in blood pressure.

Serious or Rare Side Effects

• Severe hypotension: marked blood‑pressure reduction requiring medical attention.
• Syncope: transient loss of consciousness.
• Myocardial infarction: rare but reported in susceptible patients.
• Allergic reactions: rash, itching, or swelling.
• Methemoglobinemia: rare blood‑disorder causing cyanosis.

Before initiating therapy, clinicians should evaluate cardiovascular status and concomitant medications.

• Blood pressure assessment: ensure baseline values are stable.
• Avoid concurrent nitrates: combined use can cause profound hypotension.
• Do not combine with phosphodiesterase‑5 inhibitors: risk of severe blood‑pressure fall.
• Monitor hepatic function: dose adjustment may be needed in severe impairment.
• Discontinue before major surgery: to reduce intra‑operative hypotension.
• Store at room temperature: keep in the original pack, protect from moisture and direct sunlight.

Isosorbide mononitrate may interact with several drug classes.

Major Interactions (Avoid)

• Other nitrates (e.g., nitroglycerin): additive vasodilatory effect.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): risk of severe hypotension.
• Guanylate cyclase stimulators (e.g., riociguat): excessive vasodilation.
• Methylene blue: reduces conversion to nitric oxide.

Moderate Interactions (Monitor Closely)

• Antihypertensives (ACE inhibitors, beta‑blockers): may enhance blood‑pressure lowering.
• Diuretics: additive effect on volume depletion.
• Alcohol: can increase dizziness and hypotension.
• Antihistamines: may potentiate headache and flushing.